Screw holding and feeding means for power-operated screw drivers



March 2, 1954 w POTTERTON v 2,670Q770 SCREW HOLDING AND FEEDING MEANS FOR POWER-OPERATED SCREW DRIVERS Filed July 27, 1950 2 Sheets-Sheet 1 AT TORNE YS March 2, 1954 W, POTTERTON 2,670,770

SCREW HOLDING AND FEEDING MEANS FOR POWER-OPERATED SCREW DRIVERS Filed July 27, 1950 2 Sheets-Sheet 2 S-e g,

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IN V EN TOR.

ANH. Anhui?,

ATTORNEYS WILLIAM POTTERTON Patented Mar. 2, 1 954 UNITED STATES PATENT OFFICE SCREW HOLDING AND FEEDING MEANS FOR PIOWER-OPERATED SCREW DRIVERS William Potterton, North Arlington, N. J., :as-

signor -to VAllen B. DuMont Laboratories, Inc., Passaic, N. J., a corporation of Delaware Application July 27, 1950, 'Serial No. 176,144

(Cl. 14A- 32) Thisinvention relates to portable power driven tools of the rotary type and more particularly to automatic screw drivers.

The usefulness of screw drivers of this type has been heretofore impaired by the necessity or desirability of providing pilot holes when screws are driven into relatively7 hard wood such as is used in furniture and cabinets and the like. The necessity for having a pilot holeis obviated if the screw can be held with sufficient rigidity during the rst part of the driving operation to prevent the screw from twisting while being driven.

Itis accordingly an object of my invention to provide an automatic screw driver which incorporates. means for holdingthe screw rigidly during the first part of the driving operation.

It is another object to provide a screw driver which is fully automatic in action.

It is a further object to provide a screw driver which handles without error all screws having 'a variable range of dimensions within commercial tolerances.

Another object is to provide a screw driver which is light, portable, easy to operate .and to manufacture.

In laccordance with my invention, apparatus is provided which causes screws to fall intol a cavity formed between a pair of specially shaped holding jaws. Pressure of thescrew against an 'undrilled wall then causes the screw to be rigidly clamped, driven partially lay-engagement with a Arevolving tool, and nally released from the. clamp while continuing to be driven. A feature is embodied in the apparatus for plaeingthe screwin the jaws, applying rotary force thereto and sub,- sequently disengagingv therefrom, which appara- `tus has the features of construction, combina- .in the operation thereof:

Figure 5 is a sectionview through 5--5 of Eigure '1 of the same screw driver;

Figure -6 isa view from-'an angle. lof .one ofthe specially shaped holding jawsfof tllefscrew driv- Figure 7 isy a bottom view ofthe screw-driver;

Figure 8 is a perspective view of a detail aci the head.

In the drawings, a power driven rotary Ytool :comprises a stationary barrel member I2 containing a rotating spindle', rotatable about .a longitudinal axis, of which spindle only the tool-end I3, formed in the shape of a screw driverfis visible, this part of the device being old in the art. Although a Phillips head screw driver end is shown here my invention is equally applicable to the driving of slotted and other type screws, provided the appropriate tool. end is attached to the spindle. An air hose I4 provides power to rotate the spindle in the preferred Vform, the fiow of air being controlledby a trigger valvei5 of any optional form. It will be readily apparent that my invention may alternatively incorporate a spindle powered electrically or otherwise. A sleeve vI6 forming a part of the barrel member I 2 encloses the spindle except `for thetool end I3, preventing .accidental contact therewith.

A screw track assembly Il is attached to the barrel I2 and is constricted'to longitudinal motion with respect thereto by means of a guide I8. The movable lassembly l'I comprises a screw holding magazine 22, a screw feed raceway 23. an escapement mechanism 24 and a pair of screw holding jaws 25.

A main spring 2,6, stretched between the as semb-ly I'I and the guide I8, urges .the assembly I'I in a forward longitudinal directionwith respectto the barrel I2.' Stops 21 and ZSattached tothe movable assembly Il limit the travel thereof.

The screw holding magazine 22 comprisestwo upper Ytracks 32 separated suiiiciently to clear the Shanks but not the heads of screws `33. A single lower track 34 is affixed to and separated from the upper tracks 32 by means of spacers 35 dimensioned to provide vlaterally 'constrictive clearance for the screw heads and for the guide I8. 'A movable closure member 36. atthe rear end "of `the magazine 2.2'permits'the loading of the` maglazine 22 from an auxiliaryy feed hopper and also prevents; the screws from accidentally falling out .of the rear end of the magazine. A handle 31 attached Yto the lower track 34 permits manual operation of the escapementmechanism or the rejection. of a defective screw.

The screw feed raceway 23 comprises an extension of .the tracks 32 and 34 Vfrom Vthe release .mechanism 24 to the holding jaws 25. It4 is shaped in. a gentle curve which permits the'screws to slide under gravitationaltforces frcmthelease'mechanism. to the jaws when thelongitudinal axis of the screw driver is oriented either horizontally or vertically.

The release mechanism 24 shown in different positions of its operation in Figures 2, 3 and i comprises an escapement member 4l having iingers 42 and 43 extending laterally across the upper track 32 to engage the shanks of screws and to release them one at a time into the raceway 23. The escapement member :Si is constricted to a lateral transverse motion by means of slots 44 shown in the section View of Figure 5 which engage pins 45 affixed to the lower track 34. An escapement spring 4'6 tends to maintain the escapement member 4I in the positions shown in Figures 2 and 3. A stud 4'! attached to the escapement member 4| and shown in Figure 5 provides a means for operating the escapement mechanism against the tendency of the escapement spring 46 in order to release screws one at a. time in accordance with the sequence of operation.

The holding jaws 25 are attached to the movable assembly l1 by means of jaw springs 48 'which urge the jaws inwardly. The jaw springs 48 constrict the jaws to a transverse motion with respect to the assembly l1. The jaws themselves include several features which can be seen in Figure 6, wherein that one shown is the further jaw hidden behind the nearer jaw in Figure l. In Figure 6 the inside surface 5I of the jaw is seen to define a cylindrical cavity 52 shaped to provide clearance for the tool end I3 and for the head of the screw. This cavity 52 extends forward to a tapered portion 53 and thence to a cylindrical portion 54 shaped to grip an appreciable length of the shank of the screws when the jaws are in closed position, The cavity 54 is provided with Atwo walls, a rst wall 55 extending to the inside .face of the jaws, and a less complete second wall 55 being cut back a distance sufficient so that when the jaws are in their open position, screw shanks fall between the second walls and are caught and positioned by the first walls. A

,lateral slot T, cut back in the second wall to the depth of the cavity 52, permits ingress of the screw heads when the jaws 25 are in their open position.

A second longitudinally extending slot has a Asmall diameter rear cylindrical portion 58, a tapered portion 59 and a forward large diameter ward placement thereof. The nearer jaw 25 of Figure l is a mirror image of the jaw shown in Figure 6.

An actuator 63 is shown in the view of Figure 7 attached to the forward end of the sleeve i6 and forming an integral fixed portion of the barrel l2. As seen in the onset view of Figure 8, the actuator 53 comprises a jaw actuator rod 64 and screw release actuator surface 65. The forward end of the jaw actuator rod B4 extends into the cam shaped cavity formed by the second slots 58, 59, til of the jaws 25, and terminates in a spherical cam follower 63 which bears outwardly against the second or cam slots 58, 59, 58 of each vof the jaws 25 and determines their lateral positions in accorda-nce with the relative positions of the barrel i2 and the assembly l'i. The screw release actuator surface 65 forms an angle of ap- -proximately 45 with the longitudinal axis, as ishown in the sectional view of Figure 5, and is positioned to engage the stud 4T when the assembly I1 is in a rearward position.

In operation, the magazine 22 is lled with screws 33, approximately 50 No. 6 round head screws being a typical load for a magazine of the type herein described. These screws slide down the magazine 22 guided between the tracks 32 and 34 until they engage the iinger 42 of the escapement mechanism 4l, as shown by the position of the screw 12 in Figure 2.

The escapernent mechanism 4i is then actuated by manual pulling backward of the handle 3i or by pressing the jaws 25 against a fiat surface. Either method presses the magazine into a rearward position with respect to the barrel i2 against the tension of the main spring 25. As the assembly Ii' moves backward the stud il engages the screw release actuator surface E5 urging the release mechanism 4| laterally against the pressure of the spring 4S into the position shown in Figure 4. As the release actuator moves into this position, the finger 42 regresses, permitting the screw to move forward. At the same time the second finger i3 moves against the rear portion of the screw, urging it forward to the position shown by the screw 'i3 of Figru'e 4. The screw is now free to fall forward and downward against the jaws 25 but it cannot enter the jaws until pressure against the assembly i1 is released, and the magazine is returned t0 the position shown in Figure 2. If the screw should happen to stick in the position of the screw 'i3 of Figure 4, due to static frictional forces, the return of the nger e2 when the assembly Il goes into its forward position impells it on its way down the raceway into the open holding jaws 25, as shown by the position of the screw 14 of Figure 2, where it is caught by the lower wall 55 of the cavity 52.

The screw driver is now ready for the driving opera-tion. The first driving position is that shown in Fig. 2. Here with no longitudinal pressure against the holding jaws, the main spring 25 maintains the magazine in its extreme forward position, the cam follower E5 engaging the rearward surface 58 forcing the jaws outwardly against the action of the springs 48 into their open position here shown, permitting a screw 15 to fall into that position shown in Fig. 2.

The screw driver is then pushed against a surface such as Wood into which the screw is to be driven. The wood surface engages the point of the screw, pushing its head backward into the slot 52 wherein it is Surrounded circumferentially and supported against lateral motion in any direction. The jaws 25 engage the wood surface forcing the magazine backward into a second driving position shown in Figure 3. In this position the jaws with the rest of the assembly l'l have moved backward until the cam follower 5-3 disengages the slot 52, allowing the jaws to close rmly around the shank of the screw which now is in the position of the screw 15 or Figure 3 and to support it against lateral motion in any direction.

As the screw driver jaws 25 are further pressed into a third driving position against the wood surface the assembly l1 is further pressed backward with relation to the barrel l2 until the tip of the tool end I3 engages the head of the screw. causing it to revolve and be pressed forward into the wood surface, it meanwhile having its head firmly supported against lateral motion by the groove 52 and its shank firmly supported against lateral motion by the groove 54 of the jaws, preventing twisting. It is this feature which aljaws apart into a fourth driving position shown in Figure 4, so that the screw may be driveny home for the remaining turns of its length asv shown by the position of the screw 16. In the latter stages of the driving operation, the next screw is released by the release mechanism 24 as previously described. After the rst screw has been driven home, the screw driver is removed from the wood surface and the assembly I7 again moves forward to the rst driving position where it receives the next screw and is ready to repeat the driving operation.

In order that screws be held suiciently tightly, the jaw springs 48 in the preferred form require an inward pressure in the closed position of approximately one pound. To assure opening of the jaws in the rst driving position the assembly spring 26 must exert a pressure in position 1 of about 3 pounds. The escapement spring 46, which only is required to hold the weight of the screws against gravity, need only have a tension of about 2 ounces. These tensions have been found to give completely satisfactory service in driving 5/8 inch No. 6 round head wood screws.

Although a particular embodiment of my invention has been shown and described, modicay tions thereof will be readily discernible from the foregoing description, the scope of these modications being limited in their extent by the following claims. q

What is claimed is:

1. In a portable automatic screwdriver having a barrel member containing a power driven screwdriver rotatable about a longitudinal axis, a screw holding device comprising a pair of screw holding jaws separable laterally in accordance with the relative longitudinal motion between said jaws and said barrel, a longitudinally extending cam surface common to one of said jaws, and

an actuator member connected to said barrel Y member to control separation of said jaws.

2. The device in accordance with claim 1 in which said cam surface comprises a variable depth groove extending longitudinally along the inner surface of said jaws, said grooves being tapered in the direction of the barrel.

3. In a portable automatic screwdriver, for screws having a head and a shank, separable holding jaws having a first pair of sidewalls contiguous when said jaws are closed and a second pair of side walls not contiguous when said jaws are closed, thespace between said second pair of side walls when said jaws are closed being less than the diameter of said shank to retain said shank, and said space being greater than the diameter of said shank when said jaws are opened to permit gravitational ingress of screws past said second walls in said open position.

4. In automatic screw-feed apparatus for a screw-driver, a screw-feed raceway having an escapement mechanism attached thereto and having a rest position, said escapement mechanism comprising a pair of fingers movable transversely with respect to said raceway, a rst beveledge on one of said fingers to urge a screw in one 4direction along said raceway when said escapement is moved from its rest position, and a second bevel-edge on the remaining said finger to urge said screw in the same said direction when said escapement is returned to its rest position.

5. A portable automatic screwdriver comprising a barrel member containing a power driven spindle rotatable about a longitudinal axis, and an assembly movable longitudinally with respect to said barrel member, said assembly comprising a screw holding magazine, a screw feed raceway having an end thereof joining said magazine, and screw holding jaws at least one of which is movable laterally with respect to said magazine to form an opening at the side thereof, said jaws being positioned immediately adjacent the end of said raceway removed from said magazine, said last-named end of the raceway being adjacent said side of the jaws to permit a screw from the raceway to enter said opening, a beveled surface on said movable jaw, and a cam plunger attached to said barrel member and extending in contact with said beveled surface to hold the jaws open to receive said screw through said opening.

6. A screw holding and feeding assembly for a screwdriver, comprising a plurality of jaws arranged to form an enclosure for a screw, a spring positioned to urge said jaws together, a cam surface on the inner sides of said jaws, and a cam follower positioned between said jaws and in engagement with said cam surface to hold said jaws normally open to receive a screw, said jaws being movable with respect to said cam follower to slide therealong when said assembly is pressed against an object, said cam surface being tapered to allow said jaws to be closed by said spring when said jaws are pressed against said object and caused to slide along said cam follower.

WILLIAM PO'I'IERTON.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 950,534 Hunt Mar. 1, 1910 1,231,792 Royer July 3, 1917 1,726,693 Clementson Sept. 3, 1929 1,839,490 Moeller Jan. 5, 1932 1,945,741 Gray Feb. 6, 1934 2,261,134 Blair Nov. 4, 1941 2,314,760 Blair Mar. 23, 1943 2,517,113 Jones Aug. 1, 1950 2,534,140 Moore Dec. 12, 1950 2,544,165 Krasnow Mar. 6, 1951 2,554,732 Doyle May 29, 1951 

